The present invention relates to an automatic transmission apparatus for a vehicle, which electronically controls a friction clutch interposed between an engine and a parallel shaft type gear transmission through an actuator, and a meshing position of the transmission through a speed ratio switching means.
In recent years, in order to reduce the drive load on operators of large trucks or passenger cars, an automatic transmission apparatus which can automatically select an optimal speed ratio corresponding to vehicle running conditions has been proposed.
A conventional automatic transmission apparatus has been used especially in small passenger cars, and generally comprises a speed ratio switching means for a planetary gear type transmission, in which a liquid joint (e.g., a torque converter) is interposed between an engine and the planetary gear type transmission, and which uses pressurized oil as a control medium.
When an automatic transmission apparatus for a large truck is to be developed, it is important to take the following points into consideration. Since such trucks are manufactured in smaller numbers than passenger cars, development of new torque converters is relatively more expensive.
Therefore, a conventional drive system (e.g., a friction clutch, a parallel shaft type gear transmission, etc.) and equipment for manufacturing it are preferably the same as those for passenger cars.